The present invention relates to the synthesis of butadienes and conjugated polyacetylenes from butyne-containing monomers. More particularly, the invention provides for the formation of both mono- and poly-1,4-diarylsulfonyl-1,3-butadienes from the corresponding mono- or poly-1,4-diarylsulfonyl-2-butynes under mild basic conditions in an organic solvent at ambient temperature.
Electroactive polymers have been the focus of a great deal of research in the last few years. Although organic solids have traditionally been thought of as electrical insulators, recent discoveries have demonstrated that a number of molecular crystals and organic polymers exhibit semiconductivity and even superconductivity. Due to their conductive properties, electroactive polymers have been referred to as "molecular metals". The unique properties exhibited by this new class of "molecular metals" offer great promise as conductors and semiconductors while carrying the potential benefits associated with polymers: they are inexpensive, strong, and easily processed into fibers, films, and coatings on an industrial scale. Numerous applications have been envisioned for electrically conducting organics ranging from lightweight batteries made from conducting polymer electrodes to less expensive electronic chips and semiconductors.
In general, the "molecular metals" fall into three classes. The first class consists of compounds containing metal chains. Materials in this group are characterized as either inorganic salts, such as the Krogmann salts, or metal ions, such as Pt or Ni, surrounded by organic ligands.
The second class of organic conductors, referred to as charge transfer complexes, are composed of organic crystals. Although organic crystals containing a single neutral species generally exhibit very low specific electrical conductivities, charge transfer crystals can exhibit high electrical conductivity. This group is characterized by mixed electron donor-acceptors such as tetrathiofulvalene-tetracyanoquinodimethane (TTF-TCNQ). The conductivities of these compounds generally increase upon cooling below 300.degree. K. until approximately 60.degree. K. when they undergo a Peierls transition and become semiconducting.
The third class of organic conductors, the conjugated polymers, are the subject of the present invention. Interest in this group began with the discovery that acetylene could be polymerized to a shiny black film, polyacetylene, which became highly conducting when "doped" by reaction with large amounts of strong oxidizing or reducing agents. The conductivity of the conjugated polymers is thought to be attributable to the ease of electron transport along the chain. Unfortunately, one of the principal problems presented by the conjugated polymers is that their chain rigidity and strong interchain forces tend to make them insoluble, infusible black powders.
One route which is being used to circumvent this problem is to prepare a flexible soluble precursor polymer which can be precast into films and converted into the corresponding polyacetylene. Researchers have attempted to utilize polyvinylchloride (PVC) in this manner due to the observation that upon heating, PVC releases HCl leaving a black polyacetylene-like material. Unfortunately, the resulting material is non-conductive. Presumably, the random loss of HCl pairs results in isolated Cl or H atoms which break up the conjugated sequences. Other investigators have dealt with this problem with some success by pairing up the leaving groups in the starting polymer, resulting in a more uniform polyacetylene structure. Yet, such structures often exhibit vastly different electrical properties relative to the polymer prepared by direct polymerization and they are quite difficult to chemically characterize.
Other approaches that have been investigated include modifying the polymer through copolymerization with agents such as polymethylacetylene in order to increase chain flexibility, but apparently this results in dramatic reductions in conductivity. In light of the above-mentioned problems in the development of electrical-conducting polymers, it is desirable that new methods be developed whereby polymers with increased solubility and a more uniform polymeric structure may be produced. Furthermore, it would be of additional benefit to develop methods whereby organic polymers exhibiting variations in their molecular geometry might be produced. It is possible that such geometrical variants of organic polymers might exhibit dissimilar variations in their resulting electrical properties.
In addition to the need for polymeric butadienes in the electroconductor field, butadiene-containing monomers have long been useful in the synthesis of synthetic rubber. For example, manufacture of synthetic rubber, latex paints, and nylon account for nearly all the butadiene consumed in the United States. Most of this butadiene is presently made by the expensive method involving dehydrogenation of normal butylenes and butanes or by steam cracking of naphthas. Accordingly, a less expensive and simpler method of producing monomeric butadienes is needed.